1. Field of the Invention
This invention relates to a self dumping hopper that permits safe operation of the hopper by a single operator.
2. Description of Related Art
Self dumping hoppers are typically used in industrial settings to hold and contain waste, finished materials, raw materials and/or other bulk materials or products that require loading and unloading through a dumping operation. As such, self dumping hoppers typically operate between a latched position, such as shown in FIG. 1, and a dumping position, such as shown in FIG. 2.
The self dumping hopper is typically supported on the tines of a forklift truck which enter the fork pockets in the base in the same fashion that a pallet is handled. When unlatched, gravity maintains the hopper on a gear-like track that causes it to both dump and move forward in synchronization. When the base and track are level, an empty or uniformly loaded hopper will tend to rotate forward which causes its center of gravity to move even further forward to accelerate the dumping action. The forward tilt capability of the forklift mast may be used to move the center of gravity of an empty or loaded hopper in a forward direction; conversely, rear tilt moves the center of gravity rearward which diminishes the tendency of the hopper to dump and usually urges it into a rearward rest position against its stops.
When the hopper is in its latched position it may be used for loading, storing, or transporting lading. The latched position is maintained by a latching system that is typified in FIG. 3. The latch is comprised of a hopper mounted latch pin, a frame mounted hook which is spring loaded to engage the pin, and a handle integral with the hook for manual disengagement.
Normally, self-dumping hoppers are strategically located in a factory setting and simply rest with their base on a floor or ground surface. When filled, the latched self-dumping hopper is transported as a conventional forklift load. The hopper is lifted a few inches off the surface with the forklift""s mast fully tilted rearward and it is then moved slowly to a container, dumpster or other receptacle. The hopper is positioned for dumping, the forklift is put into neutral with the parking brake set, and then the forks are raised sufficiently high to avoid horizontal interference with the container when the self-dumping hopper moves fully forward. Raising the trip lever handle manually from the ground, or manually from the forklift using a pole, and with the forklift mast vertical, begins the dump cycle under this one-person operation by unlatching the latch hook from the latch pin. Under uniform hopper loading, the hopper dumps automatically.
Occasionally, the hopper may be heavily loaded with its center of gravity biased forward. This creates a large upward force on the hook which cannot be overcome by manually lifting the trip lever handle or pushing up on it with a pole. This upward force becomes smaller and smaller as the mast is continually tilted rearward to ease this upward force. With the upward force sufficiently eased, a one-person dumping operation as previously described is again undertaken.
Normally, in the extreme position where the mast is fully tilted inboard, the unlatching resistance is provided solely by the torsion latch spring; the loaded hopper no longer contributes to the latching resistance because its center of gravity has shifted rearward. Here, the hopper easily unlatches; however, it will relatch immediately if the trip lever handle is released. Unfortunately, the full inboard mast orientation precludes dumping by a single operator. One person cannot maintain the hopper in an unlatched state and mount the forklift and lift the mast forward to dump.
The situation can be handled by a two-person dumping operation. In a two-person operation, the trip lever handle may be held in the upward or unlatched condition by a ground man while the forklift operator begins the dump cycle by tilting the mast forward.
In a one-person protocol for this situation, the operator must seek an intermediate mast tilt between xe2x80x9crearward to release the hookxe2x80x9d and xe2x80x9cnot too far rearward that the hook relatches.xe2x80x9d Trial and error is used to establish an appropriate mast angle in a range where one finds xe2x80x9crelease without relatching.xe2x80x9d
To restore the hopper to its inboard latched position after dumping, several methods may be employed: (a) the mast may be tilted rearward; (b) the forklift may be backed up slightly and then stopped abruptly; (c) a pole may be used to push up on the front of the hopper; and/or (d) the forks may be lowered to the ground and the empty hopper may be lifted by hand.
Accordingly, it is one object of this invention to provide a system for a self-dumping hopper which permits the hopper dumping to be effected as a one-person operation regardless of whether the center of gravity of the loaded fork lifted hopper is biased rearward, balanced, or biased forward when the forklift mast is tilted rearward to aid in the unlatching of the hopper to initiate its dumping.
It is another object of this invention to provide a system for a self-dumping hopper that minimizes the physical exertions required to overcome the trip lever resistance encountered when unlatching the hopper to initiate dumping, by permitting the unlatching to be done with the forklift mast fully tilted rearward regardless of whether the center of gravity of the loaded fork lifted hopper is biased rearward, balanced, or biased forward.
It is another object of this invention to provide a system for a self-dumping hopper that does not require that the forklift operator contact the hopper body when the hopper is elevated for dumping or when the hopper body is in motion while dumping.
It is another object of this invention to provide a system for a self-dumping hopper that does not require trial and error balancing procedures to initiate dumping.
It is another object of this invention to provide a system for a self-dumping hopper that does not require a pull cord for unlatching the hopper to initiate dumping, in order to achieve the objects of this invention described above.
These and other objects of this invention are addressed by a counter latch system for a self-dumping hopper to be described below. A suitable system would satisfy the following qualifications: (a) it should initiate the dumping cycle at the rearmost position of mast tilt where unlatching the hopper is least strenuous; (b) it may be optionally deployed to prevent relatching at extreme rearward mast angles, or it may be ignored to leave the original system unaltered; (c) it should be located near the hopper latching system where it can be manually engaged at ground level; (d) after the system is engaged, it must automatically cause the original latching system to return to a relatching position when the hopper moves forward, thereby permitting conventional relatching after the lading is dumped.
Several embodiments of a hopper mounted counter latch system invention will be disclosed, each of which fulfills all of the foregoing qualifications. The counter latch system invention embodiments are utilized when the forklift mast, fully tilted rearward, causes the center of gravity of the loaded fork lifted hopper to be biased rearward or be balanced. As previously described for this situation, to initiate dumping, the hopper latch trip lever handle must be typically raised manually and kept manually in the raised position, or else, if released, the counter torque of its return spring will relatch the hopper and prevent the dumping operation. Deploying the counter latch system obviates the necessity to manually keep the hopper trip lever handle in the raised position.
All embodiments of the counter latch system of the present invention accomplish this by manually interposing a blocking member into the return path of the hopper release handle after the handle is manually moved to initiate the hopper release for dumping, thereby preventing the release handle from relatching the hopper with its hopper latching hook. The counter latch blocking member is released automatically from its deployed position and returns automatically to its undeployed position when the forward motion of the dumping hopper causes the handle to clear the deployed blocking member of the counter latch. This allows the hopper release handle with its hopper latching hook to return to its relatching mode. Thus, the operation of the counter latch system of this invention does not interfere with the hopper dumping procedure and the return of the empty hopper to its latched and locked position after dumping.
A hopper with a counter latch system according to this invention is operated as follows. All loading, storing, and transporting of self-dumping hoppers proceed as normal with the hopper in a latched position and the counter latch at home base with the blocking member undeployed and flat against the hopper panel. When a filled hopper arrives at its dump site, the associated forklift has its mast fully retracted and its forks lowered. Either the forklift operator or ground personnel begin the dumping scenario by first lifting the hopper trip lever handle; minimum resistance to lifting the trip lever handle will be encountered because the mast is fully retracted. While holding the handle in one hand, the counter latch blocking member may be deployed with the other hand and the handle suitably seated against the member.
The area is cleared of ground personnel and the seated forklift operator raises the hopper to the proper dumping elevation and tilts the mast of the forklift forward to begin dumping. The forward motion of the dumping hopper causes the counter latch blocking member to release the hopper latch handle. This, in turn, causes the handle with its latching hook to automatically return to its latching ready state by its return spring, and causes the blocking member to automatically return to its undeployed state by means of a spring or gravity.
With the blocking member in its undeployed state, the empty hopper can now be returned and relatched to its upright position using the usual techniques. Thus, the counter latch is typically used only in the beginning of the dump cycle.
The counter latch system according to one preferred embodiment of this invention is mounted on the rear panel of the hopper. According to other preferred embodiments of this invention, the counter latch system may be mounted on either the latch handle or the latch base. An objective of the counter latch system for the self dumping hopper is that the latch handle is propped up after the hopper is unlatched in the extreme rearward tilt position and the counter latch is caused to return to its original position after the hopper moves forward in its dumping motion.